<template>
  <div class="pagination">
    <button :disabled="pageNo==1"
    @click="$emit('getPage',pageNo - 1)">上一页</button>
    <button 
       v-if="startNumAndEndNum.start >1"
       @click="$emit('getPage',1)"
       :class="{active:pageNo==1}"
    >
       1</button>
    <button v-if="startNumAndEndNum.start>2">···</button>

    <button 
      v-for="(page,index) in startNumAndEndNum.end" :key="index"
      v-show="page>=startNumAndEndNum.start"
      @click="$emit('getPage',page)"
      :class="{active:page==pageNo}"
    >
      {{page}}</button>
    <button v-if="startNumAndEndNum.end < totalPage-1">···</button>
    <button 
      v-if="startNumAndEndNum.end<totalPage"
      @click="$emit('getPage',pageNo + 1)"
    >
    {{totalPage}}</button>
    <button
     @click="$emit('getPage',pageNo + 1)"
     :disabled="pageNo ==totalPage"
    >
      下一页</button>

    <button style="margin-left: 30px">共 {{totalPage}}条</button>
  </div>
</template>

<script>
  export default {
    name: "Pagination",
    props:['pageNo','pageSize','total','continues'],
    computed:{
      // 总页数
      totalPage(){
        // 33.33页向上取整
        return Math.ceil(this.total / this.pageSize)
      },
      // 计算出连续的野马的其实数字和结束数字【连续也的数字至少是5】
      startNumAndEndNum(){
        const {continues, pageNo, totalPage} =this
        // 先定义两个初始和结束变量
        let start = 0,
            end = 0
        // 如果总页数不够5页
        if(continues > totalPage){
          start = 1
          end = totalPage
        }else {
        // 如果总页数够连续页【连续页可能是5/7/9】动态
          // 起始数字
          start = pageNo - parseInt(continues / 2)
          // 结束数字
          end = pageNo + parseInt(continues / 2)
          // 如果起始数字为负数或0
          if(start<1){
            start = 1
            end = continues
          }
          // 结束数字大于总页数
          if(end>totalPage){
            end = totalPage
            start = totalPage - continues + 1
          }
          return {start,end}
        }
      }
    }
  }
</script>

<style lang="less" scoped>
  .pagination {
    text-align: center;
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    };
    .active{
      background-color: skyblue;
    }
  }
</style>
